Telegraph measuring system



Oct. 6, 1925. 1.555515 R. E. PIERCE TELEGRAPH MEASURING SYSTBI FiledNov. 20, 1924 INVENTOR 12E Hence 0 ATTORNEY Patented Oct. 6, 1925.

UNITED STATES 1,555,875 PATENT OFFICE.

RALPH E. PIERCE, or nancnivronr, NEW Yon-KAssIeNon T AMERICAN TELEPHONEAND TELEGRAPH COMPANY, A CORPORATION or NEW YORK.

TELEGRAPH MEASURING SYSTEM.

Application filed November 20,1924. Serial No. 751,144.

To all whom it may concern. Y

Be it known that I, RALPH E. PIERCE, residing at Larchmont, in thecounty of WVe-st- Chester andState of New York, have invented certainImprovements in Telegraph Measuring Systems, of which the following is aspecification.

This invention relates to electrical measuring systems and particularlyto means for determining the magnitude of an interfering current in thereceiving relay of a telegraph system, which current may be set uptherein by sources either within or extraneous to such system.

In a telegraph system it is frequently desirable to determine themagnitude of the current flowing through the receiving relay of thesystem, and particularly an interfering current. One of the causes ofsuch a flow of current is unbalance between a line circuit and anartificial line, which unbalance establishes a difference of potentialacross the terminals of the receiving relay when signals are transmittedfrom the same terminal circuit with which the relay is connected.Another form of interfering current, known as cross-fire current, mayalso flow through the receiving relay from the line circuit being set uptherein by other adjacent circuits. Since currents from these and othersources interfere with the proper reception of the signaling currentswhich are transmitted over the line and intended for reception by therelay in which the interfering currents tend to flow, it is desirable todetermine the magnitude of such interfering currents in order thatproper steps might be taken to diminish their effects upon the relay.

' ()ne of the objects of thisinvention is to provide a method and meansfor measuring these interfering currents.

Other objects of this invention will be apparent from the followingdescription when read in connection with the attached drawing of whichFigure 1 shows schematically a form of embodiment of the invention formeasuring the interfering current set up in a relay by unbalance betweena line circuit and an artificial line, which interfering current arisesfrom the transmission of signals from the same terminal circuit withwhich the relay is connected; Fig. 2 shows schematically the arrangementfor measuring crossfire current-s produced in a line circuit by otheradjacent circuits; and Fig. 3 shows a modification of the measuringcircuits of Figs. 1 and 2."

In Fig. 1 the line circuit L is terminated at the stations A and B bythe bridge duplex circuits, each having an artificial line to balancethe real line. Thus at station A the line L is connected with the ratioarm 1 at the point a and the artificial line AL, with the ratio arm 2 atthe point 6. Connected with the apex of the ratio arms is-a polechanger3 having connected therewith a source 4 of a recurring signal. Bridgedacross the ratio arms between the points (land I) is a receiving relay5. Connected in parallel with the windings of the receiving relay is awinding 6 of a differential relay 7 which constitutes part of themeasuring circuit. The armature 8 of this relay is connected through thebattery'9 with one terminal of the receiver 10, the other terminal ofwhich is connected with both contacts of the said'ai mature. Anotherwinding 11 of relay 7 is connected in series with a variable resistance12 and an ammeter 13, the said connection including the contacts of areversing switch 14 to the midpoints of which is connected a battery15'. The object of this reversing switch is to control the direction ofthe flow of current through winding 11, the purpose of which will belater described. The terminal circuit at station B is preferably of thenormal bridged polar duplex type and needs no detailed description.

The method of determining the magnitude of the current fiowingthroughrelay due to lack of balance between the line L and the artificial lineAL is as follows: With the transmission of signals by 'oole changer atthe distant station E, tin: iiow of current through winding 6 will causethe armature 8 to open and close the circuit including the receiver 10,the movement of the armature depending upon the transmitted signal. Theswitch 14 is then closed in such position that current from the sourcewill fiow through the winding 11 in such direction as'to oppose theeffect upon the armature 8 of the operating current in winding 6. Theresistance 12 is then varied until the eifects of these opposingcurrents are substantially equal,which condition will be evidenced bythe absence of noise in the receiver 10. The-magnitude. of theneutralizing current may be determined either by the ammeter 13 or bythe resistance 12, assuming that the latter has been calibrated. N owsignals are sent from the pole changer 3 into the line L while signalsare being received at station A from the distant station B. If there isnot an exact balance between line L and artificial line AL interferingcurrents will flow through the receiving relay 5 and the winding 6 ofthe measuring relay 7 in addition to the operating currents from thedistant station B. The result of these interfering currents in relay 6is an occasional movement of the armature 8 which will be manifested bya sound in the telephone receiver 10. Then, if the resistance 12 isvaried to again cause the relay 7 to be unoperated, the change in theresistance'l2 to effect this result is a measure of the interferingcurrent caused by unbalance.

The arrangement shown in Fig. 2, which is intended to measure theinterfering current set up in a receiving relay by a source extraneousto the system itself, is structurally substantially that shown inFig. 1. In Fig. 2 the line circuits L and L which are the source of thisinterfering current, would be terminated by some form of transmittingand receiving circuits which might be similar to those shown inconnection with the line L. When signals are transmitted, for example,over the line L cross-fire currents will be produced in the line L andsuch currents will flow to ground at each end of the said line throughthe receiving relays connected with the terminal circuits at each end.This cross-fire current will not only flow through the receiving relay 5but also through the winding 6 of relay 7. Assuming that signals are notbeing transmitted from station B to station A over the line L, themagnitude of the cross-fire current may 'be determined in substantiallythe same manner in which the unbalance current was determined, asdescribed hereinbefore in connection with Fig. 1. That is to say, theunbalance current, flowing through the relay 5 and through the winding 6of relay 7, will be evidenced by the action of the receiver 10. Theeffect of this current upon relay 7 would then be opposed by currentthrough Winding 11, the magnitude of which may be readily determined inthe manner described. If, however, signals are being transmitted overthe line L at the same time which it is desired to measure theinterfering current, the relay 7 must be biased by an amountcorresponding to the strength of the signal current. The additionalbiasing necessary to overcome the crossfire current is a measure of thelatter current.

The arrangement shown in Fig. 3, while differing structurally from thearrangement shown in Figs. 1 and 2, operates upon substantially the sameprinciple. The relay 5 has connected therewith a winding 17 which is inaddition to the operating windings. The purpose of winding 17 is tooppose the eifect upon the armature of this relay of currents throughthe operating windings. The winding 17 is connected in series with ameter 18 and a variable resistance 19, the connection including areversingswitch 20 having a source of potential 21 connected therewith.The arrangement shown in Fig. 3 renders unnecessary the extra winding 6,because the function of that winding is performed by the operatingwinding of relay 5. A receiver and a source of potential should beconnected with the contacts and the armature of relay 5 in the manner inwhich such apparatus is connected with relay 7 of Fig. 1, but for thepurpose ofsimplicity these details have been omitted from Fig. 8.

While this invention has been disclosed as embodied in particular formsand for the performance of particular functions, it is not so limitedsince it is capable of embodiment in other forms and likewise capable ofperforming other functions without departing from the spirit and scopeof the appended claims.

What is claimed is:

1. In a system for measuring the margin of operation (.f a telegraphsystem, the combination with a line circuit of a terminal circuit havingan artificial line, bridge arms, a transmitter connected with themidpoint thereof, and a receiving relay connected across the extremitiesthereof, and means connected with the receiving relay to indicate therange of interfering current throughout which the receiving relay willcontinue to receive signals.

2. In a system for measuring the margin of operation of a telegraphsystem, the combination with a line circuit of a terminal circuit havingan artificial line, bridge arms, a transmitter connected with themidpoint thereof and a receiving relay connected across the extremitiesthereof, and a differential relay having one winding connected inparallel with the said receiving relay and having another windingconnected with a variable source of current, and indicating meansconnected with the armature of the said differential relay.

3. The method for measuring the margin of operation of the receivingrelay of the circuit defined by claim 2 which consists in applying arecurring signal to the midpoint of the said arms, varying the balanceof the said line and artificial line and determining the magnitude ofthe unbalance current.

1. In an electrical testing system, the combination with a line circuithaving a voltage set up therein of an electromagnetic device connectedwith the said line circuit, and

means connected with the said electromagnetic device to oppose theeffect therein of current received from the said line circuit, the saidlatter means having means to indicate the magnitude of the opposingcurrent.

5. In an electrical testing system, the combination with a line circuitof an artificial line, means to apply a potential to the said linecircuit and the said artificial line and a relay having one windingconnected between the said line and the said artificial line, and

having a second winding connected with a second source of potential andmeans to vary the magnitude and the direction of the current from thesaid second source through the said second Winding to oppose the efiectof the current through the said first windmg.

In testimony whereof, I have signed my name to this specification this18th day of 20 November 1924.

RALPH E. PIERCE.

